1. Field of the Invention
The present invention relates to a method for making laminated products from chemically extending liquids and laminated articles of complex geometry made thereby. The products are made by injecting a plurality of chemically extending liquids without mixing in circumferential arrangement about the axis of a mold cavity. One surface of the mold rotates with respect to the other about a common axis causing the plurality of liquids to form a layered structure which chemically extends to a solid laminate. Preferably, the layers of the laminate are formed from two liquids, the layers formed from one liquid having a different modulus of elasticity than the layers formed from the second liquid. Laminated materials made by this process have superior flex resistance after suffering a surface cut compared to corresponding homogeneous materials.
2. Description of the Prior Art
Rubber articles which are subject to stress and flexing have historically been made in a mold. Such articles include vehicle tires and rubber bushings such as spring shackle bushings. Many of these rubber articles such as tires are laminates in which the lamina consists of multiple plies of rubber and multiple plies of rubberized fabric. A laminate made according to the prior art process is first formed then the laminated product is placed in a mold and cured.
Fairly recently techniques for casting non-conventional tires from chemically extending liquids have been developed. For examples of techniques and materials used in making cast tires see U.S. Pat. Nos. 3,537,500 Beneze (1970), 3,555,141 Beneze (1971), 3,701,374 McGillvary (1972), 3,755,528 Beneze (1973), 3,860,052 Schroeder (1975), 3,879,161 McGillvary (1975), 3,902,836 McIntosh (1975), 3,932,088 Harada (1976), 3,980,606 Werner (1976) and Defensive Publication No. T-952006. While the methods of the prior art are useful in making cast tires, tires so made have a serious deficiency. That deficiency is the lack of resistance to crack propagation on repeated flexing. When a crack starts in the outer surface of a homogeneous cast tire, the crack will propagate through the tire uninterruptedly.
The concept of forming laminates by rotating the surfaces through which different thermoplastic materials simultaneously flow is known, see U.S. Pat. No. 3,737,263 Schrenk, et al. (1973). An explanation of what happens when the die of an extruder rotates while extruding different thermoplastic materials (from the die) is found in an article by Schrenk, et al. in the SPE Journal of June 1973, Volume 29, page 38. Schrenk, et al. formed films of plastic layers. When individual layers consisted of high modulus low elongation material sandwiched between softer polymers the alternate layers exhibited mutual reinforcement; see applied Science Symposium No. 24, 9-12 (1974) authored by O. W. J. Schrenk and Polymers Engineering and Science November 1969, Volume 9, No. 6, pages 393-400 Schrenk, et al.